Electrode connecting nipple and joint



June 21, 1960 R. HUND ET AL 2,941,828

ELECTRODE CONNECTING NIPPLE AND JOINT Filed Sept. 27, 1957 FIG. I.

INVENTORS. RALPH HUND & STANLEY S. WIRSIG ATTORNEYS.

United States Patent ELECTRODE CONNECTING NIPPLE AND JOINT Ralph Hund, Grand Island, N.Y., and Stanley S. Wirsig, Ridgway, Pa., assignors to Speer Carbon Company, St. Marys, Pa., a corporation of New York Filed Sept. 27, 1951, Ser. No. 686,611

5 Claims. (Cl. 287-127) This invention relates to connecting members, more commonly known as nipples, for joining cylindrical electrodes made of carbon or graphite in end to end relation. Such electrodes are employed in electric arc furnaces for conducting electric current from a holder through the electrode and by way of an are at the inner end of the electrode to metal being treated within the furnace. Such electrodes may carry several thousand amperes of electric current. In size they may range from little more than an inch up to three feet and more in diameter, and the large ones commonly are five or six feet, or more, in length and may weigh several thousand pounds.

In the operation of the furnace the electrode is gradually consumed at the arc end and this requires a more or less continuous feeding of the electrode into the furnace. In order to eliminate shutdown of the furnace for the purpose of changing or replacing electrodes which have been largely consumed it is customary to provide the ends of the electrodes with axial screw-threaded sockets, so that a new electrode section may be joined or connected, end to end, to the short length by the use of a screw-threaded nipple. Such nipples preferably are made of material having substantially the same, or similar, composition to that of the electrodes. As the electrode is gradually consumed at its inner end it will be fed intermittently by short increments into the furnace, and from time to time a new section of electrode will be joined to the outer end of the electrode by a nipple.

For satisfactory operation these joints between electrode sections should have low electrical resistance and it has been found that in order to accomplish this the adjacent ends of the electrodes should meet in a closefitting face to face relation which should be continuously maintained while the furnace is in operation. During operation of the furnace the electrode will be subjected to severe conditions of temperature and vibration and a permanently tight mechanical joint between the electrode sections is desirable not only .to keep the electrical resistance low, but also to prevent relative movement between the electrodes and the nipple which might result in unscrewing of the electrodes on the nipple, or breakage of the socket walls.

In an effort to insure a permanently tight connection between joined sections of electrode under operating conditions it has heretofore been suggested to apply to the engaging surfaces, or to portions thereof, a pitch or other bonding, binding or cementing material which will carbonize under the high temperatures to which the elecnode will be subjected in operation. The purpose is to bond and to hold the electrode sections firmly together.

A wide variety of materials has been used, and it has been suggested to apply the bonding material to the en- Patented June 21, 1960 chined surfaces and it is desirable, as pointed out here inabove, that they be in continuous firm contact with each other. In accordance with the present invention the bonding material does not enter between the opposed end faces of the electrodes, where it might increase the electrical resistance of the joint, or interfere with the desired close seating of the end faces against each other. In order to insure that the end faces of the electrode sections can engage each other snugly the nipple is made slightly shorter than the combined depths of the two sockets which are engaged by the nipple. In accordance with the present invention the bond-ing material does not enter between the ends of the nipple and the bottoms of the sockets. Bonding material at these locations has relatively little beneficial effect in maintaining a mechanically tight joint, or reducing electrical resistance. Because of the large size of the threads and the nature of the materials involved there are clearance spaces between the threaded surfaces of the nipple and the sockets in the assembled structure. In accordance with the present invention more than a major portion of these thread clearance spaces is filled with the bonding This result is accomplished by employing a nipple construction which facilitates movement of the bonding material from reservoirs into the thread clearance spaces, while effectively preventing loss of the bonding material to the engaging faces between the ends of the electrodes, and to the spaces between the ends of the nipple and the bottoms of the sockets.

It is an object of the present invention to provide an improved connecting member for joining electrodes made of carbon or graphite. It is another object of the invention to provide an improved connecting nipple having reservoir capacity for holding suilicient bonding material to fill more than a major portion of the thread clearance spaces. It is still another object of the invention to provide an improved connecting nipple with reservoirs for bonding material and means for insuring distributionof the bonding material from the reservoirs into more than a major portion of the thread clearance spaces. Another object of the invention is to provide a nipple in which the flow of bonding material to the central portion of the threaded surface of the nipple and to the end faces of the nipple is inhibited. Other objects, features and advantages of the invention will become apparent or will be pointed out as the description proceeds.

A preferred embodiment of the invention selected for the purpose of illustration and description is shown in the accompanying drawings, in which:

Figure 1 is a vertical section through an electrode joint, fragmentary portions of the joint electrodes above and below the joint being shown in elevation; and

Figure 2 is a fragmentary section, to enlarged scale, taken substantially on the line 2-2 of Figure 1.

Referring to the drawings, Figure 1 shows the upper end of an electrode 11 and the lower end of an electrode 12 joined by the screw-threaded nipple 13. The elec trodes maybe either carbon or graphite and Will sometimes be described herein simply as being made of carbonaceous material. The electrodes 11 and 12 are provided at their ends with axially disposed screw-threaded sockets for receiving and engaging the externally threaded nipple 13. In the illustrative embodiment the sockets are frusto-conical and the nipple tapers down from its longitudinal midpoint toward each end to match the sockets. It will be understood that this invention is applicable to cylindrical nipples as well. Cylindrical nipples are more commonly used for joining amorphous carbon electrodes, while tapered nipples usually are used for graphite electrodes. The size of the nipple desirably .will be proportioned to the electrode size to provide maxi- 3 mum mechanical strength as a whole, in accordance with conventional practice. The nipple is a carbonaceous body preferably having a composition substantially the same as, or similarto, that of the electrodes which are to be joined. a

Figure 1 shows an electrode joint as it might appear before being subjected to heat sufficient to cause the bonding material contained in the nipple to melt and flow from the reservoirs into the thread clearance spaces 16, where it will be carbonized by the heat. Located between the longitudinal center of the nipple and each end face thereof is at least one reservoir 14 containing bonding or binding material 15. These reservoirs are bores extending substantially transversely into the nipple, that is with their axes preferably arranged substantially normal to the longitudinal axes of the nipple. In the illustrative embodiment there is,-toward each end of the nipple, a single bore 14 extending transversely through the nipple, the axis of the bore lying on a diameter of the nipple. Depending on the number of bores andon how far they extend into the nipple, the diameter of the bore is selected so that the total volume of bonding material contained in the reservoirs will be adequate to fill more than a major portion, and preferably at least about 60% of the thread clearance spaces.

Merely by way of example, and not as a limitation, a nipple of the shape shown in the application drawings for connecting 20 inch diameter electrodes was provided with a one inch diameter bore extending transversely through each end of the nipple, about three inches from theend faces thereof. The reservoirs thus provided were found to contain sutficient bonding material forqfilling about 60%, or slightly more, of the thread clearance spaces.

For distributing the bonding material from the reservoirs into the thread clearance spaces, we provide a slot 17 in the threaded surface of the nipple at each bore end, these slots extending longitudinally of the nipple and being of a depth to extend radially inwardly slightly below the root of the threads. In a nipple of the type above described for connecting 20 inch electrodes these slots might be from about /1. inch to /2 inch, or more, in width. In the illustration the width of the slots is equal to the bore diameters. The depth of the slots below the thread root might be of the order of or more of the total slot depth, this being shown somewhat exaggcrated in the drawings for purposes ofillustration.

When the nipple becomes heated, the fusible'bonding material 15 melts and runs out of the bores 14 into the slots 17. These slots distribute the bonding material longitudinally of the nipple to those thread valleys which are intersected by, and open into, the slots. Thus, relatively short, easily traversed flow paths are provided to carry the melted bonding material from the reservoirs to a plurality of the thread clearance spaces 16.

Means are provided for diverting the bonding material from these slots 17 into the thread clearance spaces where it will be most effective in bonding the electrodes 11, 12 to the nipple 13. In order to accomplish this result, and to prevent escape of bonding material between the end faces of the electrodes and to the end faces of the nipple, the slots 17 are terminated at their inner ends short of the longitudinal center of the nipple, and at their outer ends short of the end faces of thenipple. This leaves a plurality of continuous threads at the center of the nipple and at each end of the nipple. These continuous thread sectionsserve as dams to inhibit the flow of bonding material to-the midpoint of the nipple and to the end faces of the nipple and thus they divert bonding material from the slots 17 into the intersectedthread clearance spaces. At least one, and preferably three, continuous threads are left at each end of each slot. If the number of continuous threads is'lessthan three, there QQYabcEdanger offiowof the bonding material .to the undesired areas rather than into the thread clearance spaces. If the number of continuous threads is in excess of three, the number of thread clearance spaces readily available for receiving bonding material will be cut down.

Tests have been made on electrode joints utilizing the nipple of the present invention to determine the average foot pounds of torque required to break the joints, that is, to unscrew them. Included were tests on joints in 20" electrodes using a nipple as disclosed in the drawings. The nipple had 1" diametral bores and there were three continuous threads between the ends of the slots and the longitudinal center of the nipple, and between the ends of the slots and the end faces of the nipple. Subsequent dissection showed that approximately 60%, or slightly more, of the thread clearance spaces were filled with bonding material in the completed joint. These joints, after having been heated to 1000 F., could not be broken by the application of 8000 foot pounds torque, the limit of the testing machine. Inspection disclosed that the thread surfaces at the junction between end faces of the electrodes, as well as at the ends of the nipple, were free of bonding material.

Comparative tests were made on electrode joints utilizing a nipple of design in commercial use in which the nipple has no slots extending longitudinally thereof, and in which the diametral bores were of W diameter. In these joints it was found that less than 20% of the thread clearancespaces, and sometimes only about 15%, were filled with bonding material. Under similar conditions as above, these joints could be broken, on an average, at about 5600 foot pounds torque.

By use of the nipple of this invention it is possible to fill what we believe to be an optimum percentage of the thread clearance spaces for both halves of the nip.- ple with bonding material. The slots 17 facilitate distribution of the bonding material longitudinally of the nipple. The continuous threads at the ends and center of the nipple insure distribution of the bonding material circumferentially in the thread clearance spaces between the nipple and each electrode.

In making electrode joints with the nipple of the present invention no special practice or precautions are necessary. Electrodes provided with conventional threaded sockets are screwed tightly together on to the ends of the nipple. As the electrode joint is subjected to heat, the bonding material melts and flows from the bores into the slots and through the slots and into the thread clearance spaces. Escape of the bonding material to the end surfaces of the electrodes and to the ends of the nipple where it would have less holding power is effectively prevented, and the bonding material is diverted into the thread clearance spaces. The heat causes the distributed bonding material to carbonize and form a firm connection between the threaded surfaces of the nipple and both electrode sockets throughout substantially more thana major portion of the thread clearance spaces.

The invention herein disclosed may be variously modified and embodied within the scope of the subjoined claims.

We claim:

1. A nipple for joining two carbonaceous electrodes which'have axially disposed threaded sockets in the ends thereof, the nipple comprising a carbonaceous body continuously threaded from end to end to engage the sockets for drawing the electrodes into snug end-to-end relation when they are screwed together on the nipple, there being thread clearance spaces between the threaded surfaces of thesockets and the nipple in theassernbled structure, the said carbonaceous body having between the longitudinal center thereof and each of its end faces a bore extending substantially transversely into the body, a mass of-fusiblethermosetting bonding material in each bore, the total volume of bonding material being sulficient to fill more than a major portion of the thread clearance spaces, and a slot in the threaded surface of the nipple at each bore end, these slots extending longitudinally of the nipple and being of a depth to extend radially inwardly below the root of the threads, so that when the nipple is heated and the fusible bonding material melts and runs out of the bores it will be readily transmitted through the slots longitudinally of the nipple, the said slots terminating sufiiciently short of the longitudinal center of the nipple and suiiiciently short of the end faces of the nipple to leave a plurality of helically continuous threads at each end of each slot as a dam to divert flow of the bonding material from the slots into the adjacent thread clearance spaces and circumferentially of the nipple while effectively preventing escape of bonding material to the end surfaces of the electrodes and to the ends of the nipple.

2. A nipple for joining two carbonaceous electrodes which have axially disposed threaded sockets in the ends thereof, the nipple comprising a carbonaceous body continuously threaded from end to end to engage the sockets for drawing the electrodes into snug end-to-end relation when they are screwed together on the nipple, there being thread clearance spaces between the threaded surfaces of the sockets and the nipple in the assembled structure, the said carbonaceous body having between the longitudinal center thereof and each of its end faces a bore extending substantially transversely into the body, a mass of fusible thermosetting bonding material in each bore, the total volume of bonding material being sufficient to fill more than a major portion of the thread clearance spaces, and a slot in the threaded surface of the nipple at each bore end, these slots extending longitudinally of the nipple and being of a depth to extend v radially inwardly below the root of the threads, so that when the nipple is heated and the fusible bonding material melts and runs out of the bores it will be readily transmitted through the slots longitudinally of the nipple, the said slots terminating sufficiently short of the longitudinal center of the nipple and sufficiently short of the end faces of the nipple to leave at least one helically continuous thread beyond each end of each slot as a dam to divert flow of bonding material from the slots into the adjacent thread clearance spaces and circumferentially of the nipple while effectively preventing escape of bonding material to the end surfaces of the electrodes and to the ends of the nipple.

3. A nipple for joining two carbonaceous electrodes which have axially disposed threaded sockets in the ends thereof, the nipple comprising a carbonaceous body continuously threaded from end to end to engage the sockets for drawing the electrodes into snug end-to-end relation when they are screwed together on the nipple, there being clearance space between the threaded surfaces of the sockets and the nipple in the assembled structure, the nipple having between the longitudinal center thereof and each of its end faces a bore extending substantially transversely into the body, masses of fusible thermosetting bonding material in the bores, the total volume of bonding material in the nipple being sufiicient to fill more than a major portion of the thread clearance space, and a slot in the threaded surface of the nipple at each bore end, these slots extending longitudinally of the nipple and being of a depth to extend radially inwardly below the root of the threads, so that when the nipple is heated and the fusible bonding material melts and runs out of the bores it will be readily transmitted through the slots, longitudinally of the nipple, to the thread valleys opening into the slots, the said slots terminating sufficiently short of the end faces of the nipple to leave a plurality of helically continuous threads at the outer end of each slot as a dam to inhibit flow of bonding material along the slots to the end faces of the nipple.

4. A nipple for joining two carbonaceous electrodes which have axially disposed threaded sockets in the ends thereof, the nipple comprising a carbonaceous body continuously threaded from end to end to engage the sockets for drawing the electrodes into snug end-to-end relation when they are screwed together on the nipple, there being clearance space between the threaded surfaces of the sockets and the nipple in the assembled structure, the nipple having between the longitudinal center thereof and each of its end faces a bore extending substantially transversely into the body, masses of fusible thermosetting bonding material in the bores, the total volume of bonding material in the nipple being sufiicient to fill more than a major portion of the thread clearance space, and a slot in the threaded surface of the nipple at each bore end, these slots extending longitudinally of the nipple and being of a depth to extend radially inwardly below the root of the threads, so that when the nipple is heated and the fusible bonding material melts and runs out of the bores it will be readily transmitted through the slots, longitudinally of the nipple, to the thread valleys opening into the slots, the said slots terminating sulficiently short of the longitudinal center of the nipple to leave a plurality of helically continuous threads at the inner end of each slot, at the longitudinal center of the nipple, as a dam to inhibit flow of bonding material along the slots to the central portion of the threaded surface.

5. An electrode joint comprising two carbonaceous electrodes with axially disposed threaded sockets in the ends thereof, the electrodes being arranged in end-to-end relation, a nipple of carbonaceous material threaded into the sockets and holding the electrodes with their adjacent end faces in direct mechanical and electrical contact, there being clearance space between the threaded surfaces of the sockets and the nipple in the assembled structure, the nipple having between the longitudinal center thereof and each of its end faces a bore extending substantially transversely into the body, a slot in the threaded surface of the nipple at each bore end, these slots extending longitudinally of the nipple and being of a depth to extend radially inwardly below the root of the threads, masses of fusible thermosetting bonding material in the bores adapted, when the nipple is heated, to melt and run out of the bores and be readily transmitted through the slots, longitudinally of the nipple, to the thread valleys opening into the slots, the said slots terminating sufiiciently short of the longitudinal center of the nipple and sufliciently short of the end faces of the nipple to leave a plurality of helically continuous threads at each end of each slot as dams to inhibit flow of bonding material along the slots to the ends of the nipple and to the central portion of the threaded surface, the total volume of bonding material in the bores of the nipple being sufficient to fill at least about 60% of the thread clearance space.

References Cited in the file of this patent UNITED STATES PATENTS 2,510,230 Johnson et al June 6, 1950 2,735,705 Johnson et a1. Feb. 21, 1956 2,744,945 Johnson May 8, 1956 2,810,117 Abbott Oct. 15, 1957 2,828,162 Johnson et a1. Mar. 25, 1958 

